U.S. patent number 10,079,184 [Application Number 14/730,446] was granted by the patent office on 2018-09-18 for semiconductor manufacturing apparatus and method of manufacturing semiconductor device.
This patent grant is currently assigned to TOSHIBA MEMORY CORPORATION. The grantee listed for this patent is Toshiba Memory Corporation. Invention is credited to Yuya Matsuda, Ryo Suemitsu.
United States Patent |
10,079,184 |
Matsuda , et al. |
September 18, 2018 |
Semiconductor manufacturing apparatus and method of manufacturing
semiconductor device
Abstract
According to one embodiment, a semiconductor manufacturing
apparatus includes a manufacturing processor, a signal acquisition
unit, a frequency characteristic acquisition unit, and an end-point
acquisition unit. The signal acquisition unit acquires a first
processing signal which shows a different behavior during
processing of a stacked body and after the processing of the
stacked body. The frequency characteristic acquisition unit
acquires a frequency characteristic of a noise caused by a periodic
structure of the stacked body from the first processing signal
during the processing of the stacked body. The end-point
acquisition unit detects an end point of the processing using the
acquired frequency characteristic. The manufacturing processor ends
the processing when the end point is detected.
Inventors: |
Matsuda; Yuya (Mie,
JP), Suemitsu; Ryo (Yokkaichi, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Toshiba Memory Corporation |
Minato-ku |
N/A |
JP |
|
|
Assignee: |
TOSHIBA MEMORY CORPORATION
(Minato-ku, JP)
|
Family
ID: |
56622473 |
Appl.
No.: |
14/730,446 |
Filed: |
June 4, 2015 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20160240446 A1 |
Aug 18, 2016 |
|
Foreign Application Priority Data
|
|
|
|
|
Feb 17, 2015 [JP] |
|
|
2015-028894 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01J
37/32963 (20130101); H01L 22/26 (20130101); H01J
37/32972 (20130101); H01J 2237/24564 (20130101) |
Current International
Class: |
H01J
37/32 (20060101); H01L 21/66 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
06-314668 |
|
Nov 1994 |
|
JP |
|
07-74466 |
|
Aug 1995 |
|
JP |
|
08-124904 |
|
May 1996 |
|
JP |
|
8-306648 |
|
Nov 1996 |
|
JP |
|
11-176815 |
|
Jul 1999 |
|
JP |
|
2009-28856 |
|
Feb 2009 |
|
JP |
|
2010-518597 |
|
May 2010 |
|
JP |
|
2010-219200 |
|
Sep 2010 |
|
JP |
|
WO 2008/092936 |
|
Aug 2008 |
|
WO |
|
Primary Examiner: Yu; Yuechuan
Attorney, Agent or Firm: Oblon, McClelland, Maier &
Neustadt, L.L.P.
Claims
What is claimed is:
1. A semiconductor manufacturing apparatus comprising: a
manufacturing processor configured to control each process unit
which performs processing of a stacked body, the stacked body being
formed by repeatedly stacking two or more types of films in
predetermined order above a substrate, the processing being an
etching process on the stacked body using a plasma; an emission
intensity measuring unit configured to acquire a first processing
signal, the first processing signal showing a different behavior
during the processing of the stacked body and after the processing
of the stacked body, the first processing signal being an emission
intensity of the plasma having a predetermined wavelength; a
frequency characteristic acquisition unit configured to acquire a
frequency characteristic of a noise from the first processing
signal by a Fourier transformation during the processing of the
stacked body, the noise being caused by a periodic structure of the
stacked body; a filtering frequency setting unit configured to set
a filtering frequency from the frequency characteristic; a filter
unit configured to generate a second processing signal by filtering
a component of the filtering frequency from the first processing
signal; and an end-point acquisition unit configured to detect an
end point of the processing, the end point being a time point when
a signal intensity is reduced by a predetermined degree from a
reference signal intensity at a predetermined time of the second
processing signal, wherein the frequency characteristic acquisition
unit acquires the frequency characteristic of the noise, after a
predetermined number of films are etched, and the manufacturing
processor ends the processing when the end point is detected.
2. The semiconductor manufacturing apparatus according to claim 1,
wherein the frequency characteristic acquisition unit acquires the
frequency characteristic of the first processing signal, the first
processing signal being acquired in a predetermined period after
the beginning of the processing, and the filter unit performs
filtering on the first processing signal to be acquired later by
the emission intensity measuring signal acquisition unit using the
frequency characteristic.
3. The semiconductor manufacturing apparatus according to claim 1,
wherein the frequency characteristic acquisition unit acquires
first to N-th frequency characteristics plural times in each of
first to N-th frequency calculating periods (N is an integer of 2
or more), the frequency calculating periods being set after the
beginning of the processing and before the end of the processing on
the stacked body, the filtering frequency setting unit sets a k-th
filtering frequency obtained from a k-th frequency characteristic
to a k-th frequency calculating period (k is an integer of 1 or
more and N or less), and the filter unit filters a component of the
k-th filtering frequency from the first processing signal of the
k-th frequency calculating period.
4. The semiconductor manufacturing apparatus according to claim 3,
wherein in a case where the k-th filtering frequency is equal to a
(k-1)-th filtering frequency, the filtering frequency setting unit
sets the (k-1)-th filtering frequency and does not change the
setting.
5. The semiconductor manufacturing apparatus according to claim 4,
wherein in a case where a difference between the k-th filtering
frequency and the (k-1)-th filtering frequency falls within a
predetermined range, the filtering frequency setting unit
determines that the k-th filtering frequency is equal to the
(k-1)-th filtering frequency.
6. The semiconductor manufacturing apparatus according to claim 3,
wherein in a case where the k-th filtering frequency is different
from the (k-1)-th filtering frequency, the filtering frequency
setting unit sets the k-th filtering frequency.
7. The semiconductor manufacturing apparatus according to claim 1,
wherein in a predetermined period after the beginning of the
processing, the frequency characteristic acquisition unit
repeatedly performs a process of acquiring a frequency
characteristic of the first processing signal in the predetermined
period, and the end-point acquisition unit detects a time point as
the end point of the processing when there is no frequency
component detected in the frequency characteristic.
8. The semiconductor manufacturing apparatus according to claim 7,
wherein the end-point acquisition unit sets a state where there is
no frequency component equal to or larger than a predetermined
intensity at all in the frequency characteristic as a time point
when there is no frequency component.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority
from Japanese Patent Application No. 2015-028894, filed on Feb. 17,
2015; the entire contents of which are incorporated herein by
reference.
FIELD
Embodiments described herein relate generally to a semiconductor
manufacturing apparatus and a method of manufacturing a
semiconductor device.
BACKGROUND
In a dry etching, an end point is generally determined when an
emission intensity of a plasma at a certain time falls by a
predetermined degree from the emission intensity. Herein, it is
desirable that a reference emission intensity at a certain time is
not changed.
In recent years, there is proposed a nonvolatile semiconductor
memory device having a three-dimensional structure in which memory
cells are disposed in a stacked structure. In such a structure of
the nonvolatile semiconductor device having the three-dimensional
structure, an etching process is performed on a stacked body in
which a plurality of different types of films are alternately
stacked. The emission intensity of the plasma is undulated when the
stacked body is subjected to the etching. Therefore, when an end
point detection method generally used in the dry etching is
employed, a variation occurs in an end point detection time.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view schematically illustrating an
example of a stacked body of a processing target;
FIG. 2 is a diagram schematically illustrating an example of a
configuration of a semiconductor manufacturing apparatus according
to a first embodiment;
FIG. 3 is a diagram illustrating an example of a temporal variation
of an emission intensity of a plasma obtained by an emission
intensity measuring unit;
FIG. 4 is a diagram illustrating an example of a frequency
characteristic of an emission intensity waveform;
FIG. 5 is a diagram illustrating an example of the frequency
characteristic after filtering;
FIG. 6 is a diagram illustrating an example of a denoised emission
intensity waveform;
FIG. 7 is a flowchart illustrating an example of a processing
procedure of a semiconductor manufacturing method according to the
first embodiment;
FIGS. 8A to 8D are diagrams illustrating an outline of a filtering
process in a case where there is a variation of a film thickness or
an etching rate of a substrate;
FIG. 9 is a flowchart illustrating an example of a procedure of a
semiconductor manufacturing method according to a second
embodiment;
FIG. 10 is a flowchart illustrating an example of a procedure of a
filtering frequency setting process;
FIG. 11 is a diagram illustrating an example of an outline of the
filtering frequency setting process according to the second
embodiment;
FIG. 12 is a block diagram schematically illustrating an example of
a functional configuration of a control unit of a semiconductor
manufacturing apparatus according to a third embodiment;
FIG. 13 is a diagram illustrating an example of a temporal
variation of an emission intensity of a plasma according to the
third embodiment;
FIGS. 14A to 14C are diagrams illustrating the temporal variation
of the emission intensity of the plasma of FIG. 13 after the
Fourier transformation;
FIG. 15 is a flowchart illustrating an example of a processing
procedure of a semiconductor manufacturing method according to the
third embodiment; and
FIG. 16 is a diagram schematically illustrating an example where
the semiconductor manufacturing apparatus according to the
embodiment is applied to a CMP apparatus.
DETAILED DESCRIPTION
According to one embodiment, there is provided a semiconductor
manufacturing apparatus which includes a manufacturing processor, a
signal acquisition unit, a frequency characteristic acquisition
unit, and an end-point acquisition unit. The manufacturing
processor controls each process unit which performs processing of a
stacked body which is formed above a substrate and includes a
plurality of different types of films periodically stacked thereon.
The signal acquisition unit acquires a first processing signal
which shows a different behavior in the processing of the stacked
body and after the processing of the stacked body. The frequency
characteristic acquisition unit acquires a frequency characteristic
of a noise caused by a periodic structure of the stacked body from
the first processing signal during the processing of the stacked
body. The end-point acquisition unit detects an end point of the
processing using the acquired frequency characteristic. The
manufacturing processor ends the processing when the end point is
detected.
Hereinafter, a semiconductor manufacturing apparatus and a method
of manufacturing a semiconductor device according to embodiments
will be described in detail with reference to the accompanying
drawings. Further, the invention is not limited to these
embodiments. In addition, the following description will be made
about an example where an etching process or a polishing process is
performed on a stacked body in which a plurality of different types
of films are alternately stacked. FIG. 1 is a cross-sectional view
schematically illustrating an example of the stacked body of
processing target. For example, a stacked body 15 is formed above a
semiconductor substrate (wafer) 10, and heterogeneous first and
second films 13 and 12 are alternately stacked in the stacked body
15 through an insulating film 11. As the stacked body 15 having the
heterogenous films, a stacked body of a silicon nitride film and a
silicon oxide film, a stacked body of a silicon film and the
silicon oxide film, or the like may be exemplified. Each first film
13 has almost the same thickness (for example, a thickness of
several tens nm). Each second film 12 has almost the same thickness
(for example, a thickness of several tens nm). In addition, a set
of one first film 13 and one second film 12 adjacent in a film
thickness direction will be referred to as a pair layer 14 in the
following. In addition, the lower pair layers 14 are counted from
the uppermost pair layer 14 which is set as a first layer. In a
case where the number of pair layers 14 is N, the pair layer 14 in
a k-th order from the uppermost layer is denoted as a k-th pair
layer. However, N is an integer of 2 or more, and k is an integer
of 1 or more and N or less. In FIG. 1, a mask 16 is formed to
pattern the stacked body 15 on the stacked body 15.
First Embodiment
FIG. 2 is a diagram schematically illustrating an example of a
configuration of a semiconductor manufacturing apparatus according
to a first embodiment. Further, in FIG. 2, a RIE (Reactive Ion
Etching) apparatus of a parallel plate electrode type is
exemplified as the semiconductor manufacturing apparatus. The RIE
apparatus 30 includes a chamber 31, a plasma generator 32, a power
source unit 33, a decompression unit 34, a pressure control unit
35, a gas supply unit 36, a flow control unit 37, an emission
intensity measuring unit 38, and a control unit 39.
The chamber 31 is formed in a substantially cylindrical shape of
which the both ends are closed, and has an airtight structure
capable of keeping a decompression atmosphere. The plasma generator
32 which generates a plasma P is provided in the chamber 31. In the
upper portion of the side wall of the chamber 31, a window 311 is
provided. The window 311 is made of a transparent material such as
quartz and allows light to be transmitted therethrough. Further, a
position of the window 311 is not limited to the upper portion of
the side wall of the chamber 31, and can be appropriately
changed.
The plasma generator 32 includes a lower electrode 321 and an upper
electrode 322. The lower electrode 321 is provided below an area
where the plasma P is generated in the chamber 31. In the lower
electrode 321, a holding portion (not illustrated) is provided to
hold the substrate W which is a processing object. As the holding
portion (not illustrated), for example, an electrostatic chuck may
be used. Therefore, the lower electrode 321 also serves as a
disposing portion where the substrate W is disposed and held on the
upper surface (a disposing surface). The upper electrode 322 is
provided to face the lower electrode 321.
A power source 331 is connected to the lower electrode 321 through
a blocking capacitor 332. In addition, the upper electrode 322 is
earthed. The plasma generator 32 can generate the plasma P by
supplying electromagnetic energy to the area where the plasma P is
generated.
The power source unit 33 includes the power source 331 and the
blocking capacitor 332. The power source 331 applies a
radio-frequency power of about 100 KHz to 100 MHz to the lower
electrode 321. The blocking capacitor 332 is provided to prevent
electrons that generate in the plasma P and reach the lower
electrode 321 from moving.
The decompression unit 34 is connected to the bottom of the chamber
31 through the pressure control unit 35. The decompression unit 34
decompresses the inside of the chamber 31 down to a predetermined
pressure. As the decompression unit 34, for example, a turbo
molecular pump may be used. The pressure control unit 35 controls
an internal pressure of the chamber 31 to be the predetermined
pressure based on an output of a vacuum gauge (not illustrated)
which detects an internal pressure of the chamber 31. In other
words, the chamber 31 has the area where the plasma P is generated
therein, and can keep an atmosphere decompressed lower than the
atmospheric pressure.
The gas supply unit 36 supplies an etching gas G to the area where
the plasma P is generated. The flow control unit 37 performs
control on the flow of the etching gas G supplied from the gas
supply unit 36. The flow control unit 37 adjusts a supply amount of
the etching gas G according to an instruction from the control unit
39. In the example illustrated in the drawing, the flow control
unit 37 is provided in the upper portion of the side wall of the
chamber 31 through a pipe 371. Then, the gas supply unit 36 is
connected to the flow control unit 37 through a pipe 361.
The emission intensity measuring unit 38 measures an emission
intensity of the plasma P having a predetermined wavelength
generated in the etching process. The emission intensity measuring
unit 38 includes a light receiving unit 381 and a spectrum
analyzing unit 382.
The light receiving unit 381 is provided to face the window 311. In
addition, the light receiving unit 381 and the spectrum analyzing
unit 382 are optically connected to each other through an optical
cable or the like. Therefore, the light incident on the light
receiving unit 381 through the window 311 can be transmitted to the
spectrum analyzing unit 382.
The spectrum analyzing unit 382 performs spectrum analysis on the
light generated when a plasma process is performed. In other words,
the spectrum analyzing unit 382 analyzes the light transmitted from
the light receiving unit 381 (the light generated in the chamber
31) using optical emission spectroscopy (OES). In addition, the
emission intensity with respect to the predetermined wavelength
obtained by the OES is sequentially converted into an electric
signal which is supplied to the control unit 39. The electric
signal of the emission intensity corresponds to a first processing
signal.
FIG. 3 is a diagram illustrating an example of a temporal variation
of the emission intensity of the plasma obtained by the emission
intensity measuring unit. In this drawing, the horizontal axis
represents a processing time, and the vertical axis represents the
emission intensity of the plasma having a predetermined wavelength.
In general, the emission intensity of the plasma is constant, but
noises generated when each pair layer 14 of the stacked body 15 is
etched are periodically generated, so that the emission intensity
is periodically changed as illustrated in the drawing. In addition,
the amplitude becomes smaller as time goes by. One period (for
example, a period from a certain peak to the next peak) shows that
one of the pair layers 14 (the second film 12 and the first film
13) is etched.
The control unit 39 includes a manufacturing processor 391 and an
end-point detection unit 392. The control unit 39 is implemented in
software. For example, the manufacturing processor 391 controls the
decompression unit 34, the gas supply unit 36, the power source
331, the pressure control unit 35, and the flow control unit 37
based on a predetermined recipe so as to perform the plasma
process. In the manufacturing processor 391, when the end point is
notified from the end-point detection unit 392, the plasma process
is ended.
The end-point detection unit 392 performs a predetermined process
on the electric signal (hereinafter, referred to as an emission
intensity waveform) obtained from the spectrum analyzing unit 382
so as to detect the end point. The end-point detection unit 392
includes a frequency characteristic acquisition unit 3921, a
filtering frequency setting unit 3922, a filter unit 3923, and an
end-point acquisition unit 3924.
The frequency characteristic acquisition unit 3921 obtains a
frequency characteristic of the emission intensity from the
emission intensity waveform acquired from the spectrum analyzing
unit 382. Therefore, the frequency of the periodic noise contained
in the emission intensity waveform is obtained. Herein, the
frequency is obtained after a plurality of pair layers 14 are
etched. The frequency may be calculated by the Fourier
transformation, or may be obtained directly from the emission
intensity waveform.
FIG. 4 is a diagram illustrating an example of the frequency
characteristic of the emission intensity waveform. FIG. 4
illustrates the frequency characteristic of the emission intensity
waveform of FIG. 3. In this drawing, the horizontal axis represents
the frequency, and the vertical axis represents the intensity.
Herein, a large peak in the vicinity of a frequency A [Hz] is
found, and the peak is the noise generated when the stacked body 15
is processed (that is, the noise causing periodical oscillation in
FIG. 4).
The filtering frequency setting unit 3922 determines a frequency
which is filtered based on the frequency characteristic acquired by
the frequency characteristic acquisition unit 3921. For example, in
a case where there are frequencies having a predetermined intensity
or more, a frequency in a predetermined range about each of the
frequencies having the predetermined intensity or more is set as a
filtering frequency. In addition, for example, the frequency
characteristic may be displayed in a display (not illustrated), and
a frequency range selected by a user through an input unit (not
illustrated) may be set as the filtering frequency.
FIG. 5 is a diagram illustrating an example of the frequency
characteristic after the filtering. FIG. 5 illustrates the
frequency characteristic in which the component of the set
filtering frequency is removed from the frequency characteristic of
FIG. 4 by a digital filter.
The filter unit 3923 removes the component of the set filtering
frequency from the emission intensity waveform, and generates a
denoised emission intensity waveform corresponding to a second
processing signal. The filter unit 3923, for example, is a digital
filter which removes the component of the filtering frequency set
by the filtering frequency setting unit 3922 from the emission
intensity waveform.
FIG. 6 is a diagram illustrating an example of the denoised
emission intensity waveform. In this drawing, the horizontal axis
represents the processing time, and the vertical axis represents
the emission intensity of the plasma having a predetermined
wavelength. As illustrated in the drawing, the oscillating noises
illustrated in FIG. 4 are removed, and the emission intensity
becomes almost a constant value. Further, the denoised emission
intensity waveform, for example, can be obtained from the filtered
frequency characteristic illustrated in FIG. 5 by the reverse
Fourier transformation.
The end-point acquisition unit 3924 obtains the end point from the
denoised emission intensity waveform generated by the filter unit
3923. A method of acquiring the end point can be performed by a
conventional method. For example, the emission intensity of time
t.sub.D called "Delay Time" is assumed as a reference emission
intensity. Then, the end point is defined as a time point when the
emission intensity falls by a predetermined degree of X % compared
to the reference emission intensity. The end-point acquisition unit
3924 sends a signal indicating that the end point is detected
toward the manufacturing processor 391.
Next, a semiconductor manufacturing method performed in the
semiconductor manufacturing apparatus of such a configuration will
be described. FIG. 7 is a flowchart illustrating an example of a
processing procedure of the semiconductor manufacturing method
according to the first embodiment. First, for example, the stacked
body 15 is formed in which a plurality of types of insulating films
are alternately stacked above the semiconductor substrate (wafer)
10 as illustrated in FIG. 1, and the mask 16 is formed on the
stacked body 15 (step S11). For example, the mask 16 is formed such
that a resist film is coated on the stacked body 15 and patterned
in a desired shape by lithography and development. Alternatively,
the mask 16 may be formed by disposing a hard mask on the stacked
body 15 and transferring a resist pattern onto the hard mask.
Next, the semiconductor substrate 10 is carried in the chamber 31
of the RIE apparatus 30 illustrated in FIG. 2, and disposed on the
lower electrode 321. At this time, the semiconductor substrate 10,
for example, is fixed by a mechanism such as the electrostatic
chuck. Thereafter, the decompression unit 34 and the pressure
control unit 35 are controlled by the manufacturing processor 391
such that the pressure in the chamber 31 becomes a predetermined
pressure.
When the state in the chamber 31 becomes a predetermined state (for
example, the predetermined pressure), the manufacturing processor
391 starts the plasma process on the stacked body 15 disposed above
the semiconductor substrate 10 (step S12). At this time, the
decompression unit 34, the pressure control unit 35, the gas supply
unit 36, and the flow control unit 37 are controlled by the
manufacturing processor 391 such that the pressure of the etching
gas in the chamber 31 becomes a predetermined value. In addition,
the radio-frequency power is applied to the lower electrode 321
from the power source 331 through the blocking capacitor 332, and
the plasma P is generated between the lower electrode 321 and the
upper electrode 322. Then, the etching is performed using the
etching gas in a plasma state.
During the plasma process, the emission intensity measuring unit 38
monitors the intensity of the plasma having a predetermined
wavelength through the window 311 provided in the chamber 31 (step
S13). The emission intensity measuring unit 38 sends the emission
intensity waveform to the frequency characteristic acquisition unit
3921. Further, the monitoring of the emission intensity of the
plasma is continuously performed until the plasma process is
ended.
Next, when a predetermined number of pair layers 14 are etched
after the beginning of processing, the frequency characteristic
acquisition unit 3921 obtains the frequency characteristic of the
emission intensity waveform (step S14). Therefore, for example, the
frequency characteristic of the emission intensity waveform as
illustrated in FIG. 4 is obtained.
Thereafter, the filtering frequency setting unit 3922 selects the
filtering frequency from the frequency characteristic of the
obtained emission intensity waveform (step S15). In the example of
FIG. 4, the frequencies in a range from A1 [Hz] to A2 [Hz] are
filtered in order to remove the peak in the vicinity of A [Hz].
Therefore, the frequency characteristic after the digital filter
illustrated in FIG. 5 is obtained.
Next, the filter unit 3923 generates the denoised emission
intensity waveform obtained by removing the component of the
filtering frequency from the obtained emission intensity waveform
using the digital filter (step S16). For example, the oscillating
noise illustrated in FIG. 3 is removed, and the denoised emission
intensity waveform illustrated in FIG. 6 in which the emission
intensity is almost a constant value is generated.
Thereafter, the end-point acquisition unit 3924 acquires the
emission intensity at time t.sub.D in the denoised emission
intensity waveform, and sets the emission intensity as the
reference emission intensity (step S17). Next, the filter unit 3923
removes the component of the filtering frequency from the emission
intensity waveform continuously sent from the spectrum analyzing
unit 382 using the digital filter (step S18).
Thereafter, the end-point acquisition unit 3924 determines whether
the emission intensity observed at the present time in the denoised
emission intensity waveform is decreased by a predetermined degree
or more from the reference emission intensity (step S19). In a case
where the current emission intensity is not decreased by the
predetermined degree from the reference emission intensity (No in
step S19), the etching is not ended yet, so that the procedure
returns to step S18 and the monitoring goes on.
In addition, in a case where the current emission intensity is
decreased by the predetermined degree or more from the reference
emission intensity (Yes in step S19), the etching is considered to
be ended, and the detection of the end point is notified to the
manufacturing processor 391 (step S20).
When the notification of the detection of the end point is
received, the manufacturing processor 391 ends the plasma process
(step S21). Herein, the control is made such that the supplying of
the radio-frequency power from the power source 331 to the lower
electrode 321 is stopped, and the supplying of the gas from the gas
supply unit 36 into the chamber 31 is stopped. Then, the
semiconductor substrate 10 is carried out of the lower electrode
321, and the process is ended. Thereafter, a process of
manufacturing a predetermined semiconductor device is performed
using the etched stacked body 15.
Further, the above-mentioned process is desirably performed
whenever the substrate is processed. FIGS. 8A to 8D are diagrams
illustrating an outline of a filtering process in a case where
there is a variation of a film thickness or an etching rate of a
substrate. FIG. 8A illustrates the emission intensity waveform,
FIG. 8B illustrates the frequency characteristic of the emission
intensity waveform, FIG. 8C illustrates the frequency
characteristic of the emission intensity waveform which is
subjected to the filtering by the digital filter, and FIG. 8D
illustrates the denoised emission intensity waveform.
The solid lines in FIGS. 8A to 8D indicate the emission intensity
waveform or the frequency characteristic in the stacked body 15 of
a certain semiconductor substrate 10. The semiconductor substrate
10 is set as a reference substrate. In a case where a substrate has
a film thickness of the pair layer 14 thinner than that of the
reference substrate or has an etching rate faster than that of the
reference substrate, the frequency of the noise becomes smaller
than the case of the reference substrate. Therefore, as illustrated
in FIG. 8B, a noise 800 is shifted to the left side (that is, a
smaller frequency) from the peak of the reference substrate. As a
result, as illustrated in FIG. 8C, the filtering frequency is also
shifted to be a smaller frequency. Then, as illustrated in FIG. 8D,
the noise of the semiconductor substrate 10 can be removed by
removing the component of the filtering frequency using the digital
filter.
On the other hand, in a case where a substrate includes the pair
layer 14 having a film thickness larger than that of the reference
substrate or has the etching rate slower than that of the reference
substrate, the frequency of the noise becomes larger than the case
of the reference substrate. Therefore, as illustrated in FIG. 8B,
the noise 800 is shifted to the right side (that is, a larger
frequency) from the peak of the reference substrate. As a result,
as illustrated in FIG. 8C, the filtering frequency is also shifted
to be a larger frequency. Then, as illustrated in FIG. 8D, the
noise of the substrate can be removed by removing the component of
the filtering frequency using the digital filter.
In this way, the film thickness or the etching rate may be
different depending on the semiconductor substrate 10, but when the
method of this embodiment is employed for the etching of each
semiconductor substrate 10, it is possible to adjust the difference
of the film thickness or the etching rate of each semiconductor
substrate 10.
In the first embodiment, when a predetermined number of pair layers
14 are processed after the beginning of the processing, the
frequency of the noise is obtained, and the component of the
frequency is removed from the emission intensity waveform using the
digital filter. Therefore, the emission intensity of the plasma
becomes substantially constant, so that it is possible to employ an
end point detection method in which the end point is detected in a
case where the emission intensity is decreased by the predetermined
degree or more from the reference intensity. As a result, it is
possible to detect the end point of the etching process
accurately.
In addition, since the filtering frequency is obtained from the
emission intensity waveform whenever the semiconductor substrate 10
is processed and the end point is detected, it is possible to
effectively cope with a case where the film thickness varies in
each semiconductor substrate 10 or a case where the etching rate is
changed.
Second Embodiment
In the first embodiment, the description has been made on an
assumption that there is no variation of the film thickness or the
etching rate is not changed in one substrate. Therefore, when a
predetermined number of pair layers are completely processed after
the beginning of the processing, the filtering frequency is
obtained, and the subsequent filtering of the emission intensity
waveform is performed at the filtering frequency. However, in a
case where a variation occurs in the film thickness or a case where
the etching rate is changed in one substrate, it is not possible to
clearly remove the noise. Then, the description in a second
embodiment will be made about that the end point in the
semiconductor manufacturing process is detected in a case where the
variation occurs in the film thickness or in a case where the
etching rate is changed in one substrate.
The configuration of a semiconductor manufacturing apparatus
according to the second embodiment is different in the function of
the filtering frequency setting unit 3922 of the first embodiment.
The filtering frequency setting unit 3922 sets the filtering
frequency plural times during an etching process (a period until
the processing is ended in the stacked body 15 after the beginning
of the processing). For example, when the processing proceeds up to
an a-th pair layer after the beginning of the processing, a first
setting process of the filtering frequency is performed. Next, when
the processing proceeds from a (a+1)-th pair layer up to a b-th
pair layer, a second setting process of the filtering frequency is
performed. Thereafter, similarly, an N-th setting (N is an integer
of 3 or more, and a and b are integers of 2 or more and N or less,
satisfying a<b) of the filtering frequency is finally
performed.
In addition, the filtering frequency setting unit 3922 determines
whether the filtering frequency thus set is equal to the
currently-used filtering frequency. In a case where both filtering
frequencies are equal to each other, the currently-used filtering
frequency is used, and otherwise the newly-set filtering frequency
is used for the emission intensity waveform which is monitored
later on. Further, the other components are identical with or
similar to those of the first embodiment, and thus the descriptions
thereof are not repeated.
Next, the semiconductor manufacturing method using the
semiconductor manufacturing apparatus according to the second
embodiment will be described. FIG. 9 is a flowchart illustrating an
example of a procedure of a semiconductor manufacturing method
according to the second embodiment.
Similarly to steps S11 to S13 of FIG. 7 of the first embodiment,
the semiconductor substrate 10 in which the mask 16 is formed on
the stacked body 15 is fixed onto the lower electrode 321 of the
semiconductor manufacturing apparatus, a predetermined pressure is
set in the chamber 31, and the etching gas is introduced therein.
Thereafter, a plasma is generated and the plasma process starts,
and then the emission intensity of the plasma is monitored (steps
S31 to S33).
Next, the frequency characteristic acquisition unit 3921 acquires a
first frequency characteristic from a first emission intensity
waveform in a first frequency calculating period after the
beginning of the processing (step S34). The first frequency
calculating period, for example, is a period where the etching is
performed on the a-th pair layer after the beginning of the
processing. Thereafter, the filtering frequency setting unit 3922
selects a first filtering frequency from the first frequency
characteristic of the first emission intensity waveform (step
S35).
Thereafter, the filter unit 3923 generates a first denoised
emission intensity waveform obtained by removing the component of
the first filtering frequency from the first emission intensity
waveform using the digital filter (step S36).
Thereafter, a setting process of the filtering frequency in the
next frequency calculating period is performed (step S37). FIG. 10
is a flowchart illustrating an example of a procedure of a
filtering frequency setting process. First, the frequency
characteristic of the emission intensity waveform is obtained in
the next frequency calculating period (step S51). Next, the
filtering frequency setting unit 3922 acquires the filtering
frequency from the frequency characteristic of the obtained
emission intensity waveform (step S52). In addition, the filtering
frequency setting unit 3922 determines whether the acquired
filtering frequency is equal to the filtering frequency in the
previous frequency calculating period (step S53).
Further, the acquired filtering frequency and the filtering
frequency in the previous frequency calculating period may be
completely matched with each other, and in a case where the
filtering frequency in the previous frequency calculating period
and the acquired filtering frequency are present in a predetermined
range, both filtering frequencies may be considered as the matched
frequency.
In a case where the filtering frequency is equal to the filtering
frequency of the previous frequency calculating period (Yes in step
S53), the filtering frequency setting unit 3922 does not change the
filtering frequency of the previous frequency calculating period
(step S54). In addition, in a case where the filtering frequency is
different from the filtering frequency of the previous frequency
calculating period (No in step S54), the filtering frequency
setting unit 3922 selects the acquired filtering frequency (step
S55). Then, the filtering frequency setting process is ended, and
the process returns to FIG. 9.
Returning to FIG. 9, thereafter, the filter unit 3923 removes the
component of the filtering frequency selected from the emission
intensity waveform acquired after the next frequency calculating
period using the digital filter (step S38). Further, in steps S37
to S38 performed after the first frequency calculating period, the
next frequency calculating period becomes a second frequency
calculating period, and the acquired filtering frequency becomes a
second filtering frequency.
Thereafter, the filtering frequency setting unit 3922 determines
whether there is a next frequency calculating period (step S39). In
a case where there is a next frequency calculating period (Yes in
step S39), the procedure returns to step S37. In addition, in a
case where there is no next frequency calculating period (No in
step S39), the intensity of the denoised emission intensity
waveform at a certain time is set as the reference emission
intensity (step S40).
Next, the filter unit 3923 removes the component of the filtering
frequency from the emission intensity waveform continuously sent
from the spectrum analyzing unit 382 using the digital filter (step
S41). Thereafter, the end-point acquisition unit 3924 determines
whether the emission intensity observed at the present time in the
denoised emission intensity waveform is decreased by a
predetermined degree or more from the reference emission intensity
(step S42). In a case where the current emission intensity is not
decreased by the predetermined degree or more from the reference
emission intensity (No in step S42), the etching is not ended yet,
so that the procedure returns to step S41 and the monitoring goes
on.
In addition, in a case where the current emission intensity is
decreased by the predetermined degree or more from the reference
emission intensity (Yes in step S42), the etching is assumed to be
ended, and the detection of the end point is notified to the
manufacturing processor 391 (step S43). Similarly to step S21 of
FIG. 7 of the first embodiment, when the notification of the
detection of the end point is received, the manufacturing processor
391 ends the plasma process (step S44). Then, the process is ended.
Thereafter, a process of manufacturing a predetermined
semiconductor device is performed using the etched stacked body
15.
FIG. 11 is a diagram illustrating an example of an outline of the
filtering frequency setting process according to the second
embodiment. In this drawing, the monitored emission intensity
waveform is illustrated. In this drawing, the horizontal axis
represents time elapsing after the beginning of the processing, and
the vertical axis represents the emission intensity of the plasma.
As illustrated in this drawing, a period from time 0 (the beginning
of the processing) to time t.sub.21 is the first frequency
calculating period, a period from time t.sub.21 to time t.sub.22 is
the second frequency calculating period, and a period from time
t.sub.22 to time t.sub.23 is a third frequency calculating period.
In other words, the filtering frequency setting process is
performed three times. For example, in a case where the first to
third filtering frequencies calculated in the first to third
frequency calculating periods are different from each other, the
first to third filtering frequencies are set in the first to third
frequency calculating periods, respectively. In addition, in a case
where the first and second filtering frequencies are equal and the
third filtering frequency is different, the first filtering
frequency is set in the first and second frequency calculating
periods, and the third filtering frequency is set in the third
frequency calculating period.
Further, the description has been made about that the reference
emission intensity is obtained after it is determined that there is
no next frequency calculating period of step S39, but the reference
emission intensity may be obtained at any timing as long as the
first denoised emission intensity waveform is obtained by removing
the noise at the first filtering frequency of step S36 and it is
not determined yet whether the end point is detected in step
S42.
In the second embodiment, a plurality of frequency calculating
periods are provided, and the filtering frequency of the monitored
emission intensity is obtained at each frequency calculating
period. In addition, it is determined whether the obtained
filtering frequency is equal to the previous frequency calculating
period. In a case where both filtering frequencies are equal to
each other, the filtering frequency of the previous frequency
calculating period is used, and otherwise the obtained filtering
frequency is set. Therefore, in one semiconductor substrate 10,
even in a case where there is a variation of the film thickness in
the stacked film or in a case where the etching rate varies due to
the etching gas, it is possible to remove the periodic noise from
the original waveform of the emission intensity with a high
accuracy. As a result, the same effect as that of the first
embodiment can be obtained.
Third Embodiment
In the first and second embodiments, the frequency characteristic
of the monitored emission intensity is acquired, the filtering
frequency is obtained from the frequency characteristic, and the
end point is detected using the emission intensity waveform from
which the noise is removed. In a third embodiment, the description
will be made about a case where the end point is detected by
another method.
FIG. 12 is a block diagram schematically illustrating an example of
a functional configuration of the control unit of a semiconductor
manufacturing apparatus according to the third embodiment. Further,
the configuration of the semiconductor manufacturing apparatus
other than the control unit 39 are the same as those illustrated in
FIG. 2, and thus the description thereof will not be repeated.
The control unit 39 of the semiconductor manufacturing apparatus
according to the third embodiment includes the manufacturing
processor 391 and the end-point detection unit 392. The control
unit 39 is implemented in software. The manufacturing processor 391
is the same as that described in the first embodiment. The
end-point detection unit 392 includes the frequency characteristic
acquisition unit 3921 and the end-point acquisition unit 3924.
The frequency characteristic acquisition unit 3921 calculates a
frequency of the noise from an emission intensity signal acquired
from the spectrum analyzing unit 382 for each predetermined period
through the Fourier transformation.
The end-point acquisition unit 3924 measures the frequency acquired
by the frequency characteristic acquisition unit 3921 for each
predetermined period, determines that the etching is ended in a
case where no frequency in a certain period is output, and
transfers the result to the manufacturing processor 391. In
practice, it is rare for the frequency not to be output at all, so
that a case where all the calculated frequencies are less than a
predetermined intensity may be considered as a case where no
frequency is output.
A principle of the end point detection in the etching according to
the third embodiment will be described. As described above, in the
etching process of the stacked body 15, when a periodic stacked
structure is etched, the emission intensity periodically changes
like a sinusoidal wave. However, when it goes to the film (the
insulating film 11 in FIG. 1) below the stacked body 15 (that is,
outside the stacked body 15), the frequency is not output. Then, in
the third embodiment, a time point when the frequency is not output
is considered as the end point of the etching.
FIG. 13 is a diagram illustrating an example of the temporal
variation of the emission intensity of the plasma according to the
third embodiment. FIGS. 14A to 14C are diagrams in which the
temporal variation of the emission intensity of the plasma of FIG.
13 is subjected to the Fourier transformation, in which FIG. 14A is
a diagram illustrating an example of a relation between the
frequency and the time when the stacked film is etched, FIG. 14B is
a diagram illustrating an example of a state where the stacked film
is being etched, and FIG. 14C is a diagram illustrating an example
of a state when the etching of the stacked film is ended.
When the stacked body 15 illustrated in FIG. 1 is etched, as
illustrated in FIG. 13, a time (period) taken for the etching of
one layer of the pair layer 14 becomes longer (the etching rate
becomes larger) as it goes from a shallow area to a deep area. This
means that the frequency of the noise superimposed on the emission
intensity waveform becomes smaller as time goes by. For example, in
the example of FIG. 13, the period is 10 seconds and the frequency
is 0.1 Hz in a first period from the beginning of the processing to
time t.sub.31; the period is 20 seconds and the frequency becomes
0.05 Hz in a second period from time t.sub.31 to time t.sub.32; and
the period is 30 seconds and the frequency becomes 0.03 Hz in a
third period from time t.sub.32 to t.sub.33. Then, finally, the
period approaches infinity, and the frequency becomes 0 Hz. This
state is illustrated in FIG. 14A. In FIG. 14A, when there is no
output frequency, it can be determined that the etching is
ended.
In the third embodiment, the frequency characteristic acquisition
unit 3921 performs the Fourier transformation on the emission
intensity waveform for each predetermined period. The result of the
Fourier transformation performed on the first to third periods of
FIG. 13 is illustrated in FIG. 14B. As illustrated in the drawing,
the frequency moves in a direction toward "0" as it goes from the
first period to the third period. Thereafter, similarly the Fourier
transformation of the emission intensity waveform is performed for
each predetermined period, and no output is found as illustrated in
FIG. 14C. The end-point acquisition unit 3924 determines that the
end point is detected when the state of no output frequency is
detected. Further, as described above, the frequency of some
intensity is calculated in practice. However, when the intensity is
less than a certain threshold I.sub.th having no influence on the
end point detection, the corresponding frequency is neglected, so
that the end point detection can be performed.
FIG. 15 is a flowchart illustrating an example of a processing
procedure of a semiconductor manufacturing method according to the
third embodiment. Similarly to steps S11 to S13 of FIG. 7 of the
first embodiment, the semiconductor substrate 10 in which the mask
16 is formed on the stacked body 15 is fixed onto the lower
electrode 321 of the semiconductor manufacturing apparatus, a
predetermined pressure is set in the chamber 31, and the etching
gas is introduced therein. Thereafter, a plasma is generated and
the plasma process starts, and then the emission intensity of the
plasma is monitored (step S71 to S73).
Next, the frequency characteristic acquisition unit 3921 determines
whether a predetermined period elapses after the beginning of the
processing (step S74). The predetermined period is desirably set to
be larger than time taken for etching one layer of the pair layer
14. In a case where the predetermined period does not elapse (No in
step S74), it enters a standby state. In addition, in a case where
the predetermined period elapses (Yes in step S74), the frequency
characteristic acquisition unit 3921 obtains the frequency
characteristic of the emission intensity waveform of the
predetermined period (step S75). For example, the frequency
characteristic can be obtained by the Fourier transformation. The
filter unit 3923 determines whether the intensities of all the
frequencies are less than a predetermined value (step S76).
In a case where the intensities of all the frequencies are larger
than the predetermined value (No in step S76), it is determined
whether the next predetermined period elapses (step S77). In a case
where the predetermined period does not elapse (No in step S77), it
enters the standby state. In addition, in a case where the
predetermined period elapses (Yes in step S77), the process returns
to step S75.
In a case where it is determined in step S76 that the intensities
of all the frequencies are less than the predetermined value (Yes
in step S76), the filter unit 3923 considers that the etching is
ended, and notifies the detection of the end point to the
manufacturing processor 391 (step S78). When the notification of
the detection of the end point is received, the manufacturing
processor 391 ends the plasma process similarly to step S21 of FIG.
7 of the first embodiment (step S79). Then, the process is ended.
Thereafter, a process of manufacturing the predetermined
semiconductor device is performed using the etched stacked body
15.
In the third embodiment, the monitored emission intensity waveform
is subjected to the Fourier transformation for each predetermined
period, and it is determined whether the intensities of all the
resultant frequencies are equal to or less than the predetermined
value. Then, in a case where the intensities of all the frequencies
are equal to or less than the predetermined value, the end point of
the etching is detected and notified to the manufacturing processor
391, and then the plasma process is ended. Therefore, even in a
case where the emission intensity is periodically changed, it is
possible to accurately obtain the end point of the etching
process.
Further, the above description has been made about an example where
the parallel flat electrode type of the RIE apparatus is employed
as the semiconductor manufacturing apparatus, and other types of
the RIE apparatuses such as an ICP (Inductive Coupling Plasma) type
of the RIE apparatus and a magnetron type of the RIE apparatus may
be employed. In addition, a CDE (Chemical Dry Etching) apparatus
may be employed as the semiconductor manufacturing apparatus. In a
case where the CDE apparatus is employed, the configuration is the
same as that of the above-mentioned RIE apparatus.
Furthermore, a CMP (Chemical Mechanical Polishing) apparatus may be
employed as the semiconductor manufacturing apparatus. FIG. 16 is a
diagram schematically illustrating an example where the
semiconductor manufacturing apparatus according to an embodiment is
applied to the CMP apparatus. The CMP apparatus 50 includes a
polishing unit 51 which performs a polishing process of the
substrate W and a control unit 52 which controls the process in the
polishing unit 51.
The polishing unit 51 includes a polishing table 511 which is
rotatable, a polishing pad 512 which is bonded on the polishing
table 511 through an adhesive layer (not illustrated), a polishing
head 513 which is disposed above the polishing pad 512 and holds
the substrate W, a chemical solution supply nozzle 514 which
supplies a chemical solution such as polishing slurry 515 at the
time of polishing, a dresser 516 (for example, a diamond disk)
which is disposed above the polishing pad 512 and dresses the
polishing pad 512, and a torque value measuring unit 517 which
measures a value of torque (a force making the polishing head 513
rotate), sequentially converts the torque value into an electric
signal, and outputs the electric signal to the control unit. The
electric signal (the first processing signal) indicating the torque
value obtained by the torque value measuring unit 517 has the same
waveform as that of the emission intensity of the plasma described
above.
The control unit 52 includes a manufacturing processor 521 and an
end-point detection unit 522. The control unit 52 is implemented in
software. The manufacturing processor 521, for example, controls
the respective processors of the polishing unit 51 according to a
recipe generated in advance so as to perform a CMP process. When
the notification of the end point from the end-point detection unit
522 is received, the manufacturing processor 521 ends the CMP
process.
The end-point detection unit 522 performs a predetermined process
on the electric signal corresponding to the torque value of the
polishing head 513 acquired from the torque value measuring unit
517 according to the same procedure as the end-point detection unit
392 described in the first to third embodiments, and detects the
end point. The end-point detection unit 392 described in any one of
the first to third embodiments can be applied to the end-point
detection unit 522.
In this way, even when the stacked body 15 in the CMP apparatus 50
is polished, it is possible to detect the end point as described
above in the first to third embodiments.
In addition, the above description has been made about an example
where two types of films are alternately stacked on the stacked
body 15. However, the above embodiments are not limited to this
configuration. For example, even in a case where three types of
films are periodically stacked on the stacked body 15 in a
predetermined order, the above-mentioned embodiments can be
applied.
While certain embodiments have been described, these embodiments
have been presented by way of example only, and are not intended to
limit the scope of the inventions. Indeed, the novel embodiments
described herein may be embodied in a variety of other forms;
furthermore, various omissions, substitutions and changes in the
form of the embodiments described herein may be made without
departing from the spirit of the inventions. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
inventions.
* * * * *